Herbs perennial, mat- or cushion-forming, caulescent or acaulescent; caudex superficial. Hairs malpighian. Stems several to numerous, sometimes obscured by stipules. Stipules connate-sheathing. Leaves palmately trifoliolate (except sometimes 5-foliolate in A. sericoleucus), petiolate. Racemes subumbellate or loosely flowered, exserted or included in stipular sheath, flowers ascending. Calyx tubes campanulate, campanulate-turbinate, or subcylindric. Corollas usually pink-purple, rarely white, banner recurved through 40–90°, keel apex round, bluntly deltate, or subacutely triangular, sometimes ± beaklike. Legumes deciduous, sessile, ascending to recurved, invested by calyx or partly exserted, lanceoloid- or ovoid-ellipsoid, straight, slightly compressed or obscurely 3-sided compressed, unilocular. Seeds (2 or)6–12.

Distribution

c, w United States.

Discussion

Species 4 (4 in the flora).

Section Sericoleuci is distributed in northeastern Colorado, western Kansas, southeastern Montana, western Nebraska, western South Dakota, northeastern Utah, and Wyoming.

D. Isely (1998) placed the species in sect. Sericoleuci and sect. Orophaca in the genus Orophaca (Torrey & A. Gray) Britton, emphasizing the isolated nature of the group, the trifo­li­olate leaves, and the base chromosome number of x = 12. M. F. Wojciechowski et al. (1999) found that A. aretioides and A. sericoleucus, and presumably other species Isley treated in Orophaca, are clearly nested within North American Astragalus and not distinct from it.

Selected References

None.

Lower Taxa

Astragalus aretioides, Astragalus barrii, Astragalus sericoleucus, Astragalus tridactylicus